U.S. Pat. No. 5,525,491 A discloses serine-rich peptide linkers for linking two or more protein domains to form a fused protein.
U.S. Pat. No. 7,271,149 B2 discloses glycine-rich peptide linkers for GLP-1 fusion proteins.
US 2007/0135338 A1 discloses GLP-1 CH1 deleted mimetibody polypeptides incorporating a linker sequence that contains serine and glycine.
US 2010/0292133 A1 and US 2011/0082079 A1 disclose GLP-1 derivatives incorporating as a linker an amino acid except Cys, or a dipeptide such as Gly-Lys.